Land is surveyed to create a contour map or other graphical representation of the land based on linear and angular measurements. According to conventional practice, surveying is at least a two person job, with one person operating a measuring instrument, transit or total station from a generally stationary position and the other person transporting and positioning a rod or target that is sighted by the measuring instrument. To create a graded surface from a track of land, the land is marked or staked.
Relatively crude instruments were once used for land surveying. Surveyors used simple optical theodolites as transits to determine the horizontal azimuth angles and the vertical elevation angles between survey points. Chains and tape measures were used to measure the distance between the theodolite and a point to be established. Telescopic devices, e.g., horizontal levels and graduated rods were also used to determine the actual elevation of a point or location from a reference position.
Referring to FIG. 1, the transit 10, also known as the measuring instrument or station, is positioned at a known distance and angle from a reference or bench mark position. The target 11, also referred to as the “rod,” is positioned at a location where it is leveled by the operator to ensure accurate measurements. As shown in FIG. 2, the target 11a may be placed upon a tripod 12 which includes a bubble measure (not shown) to ensure that the tripod 12 is level. At each such location, the distance and angle of the target 11a with respect to the position of the transit 10 is determined and recorded. Distances were traditionally measured manually with a steel tape or chain.
In contrast, modern transits may incorporate electronic distance measurement (EDM) technology in the form of laser and/or infrared beams in combination with retro-reflective devices, such as corner cube prisms, in the determination of precise distances. In addition to or as an alternative to EDM, modern transits can incorporate global positioning satellite (GPS) technology. FIG. 3 schematically illustrates a modern transit station 10a that may be linked optically to the target reflector 13 as well as being communicatively linked to a GPS 14 and a receiver 15 mounted to a tripod 12a. The transit 10a also includes a receiver 19. The target receiver 15 typically includes a display 16 and/or a speaker 17, both of which can provide an indication to the rod operator that the target 13 and rod 11b are disposed in the correct location for marking. It will be noted that the target 13 is mounted directly above the rod 11b. The reflector 13 may also include some sort of transmitter for communicating with the GPS system 14 and/or the transit 10a. The target receiver 15 may also be optically or otherwise communicatively linked to the target 13, GPS system 14 and the transit 10a. The beams originating at the transit 10a are reflected by the target/reflector 13 as parallel collinear beams of energy back to the transit receiver 19. Phase angle measurements and timing circuits allow the exact distance between the transit 10a and reflector 13 to be precisely determined and displayed. Such electronic instruments have greatly improved the accuracy of the measurements and the setting of points. EDM devices can be used to provide accurate measurements even though the reflector or prism targets 13 are two or three thousand feet away from the transit 10a. 
Still referring to FIG. 3, to mark a point, the target 13 is positioned near a location to be marked, and its position is determined by the transit 10a. If the target 13 is not exactly positioned at the location to be marked, the position is noted and the target 13 is repositioned and re-measured until the measuring transit 10a and/or target receiver 15 verifies that the tripod 12a is positioned at the precise location to be marked. A stake 21 or other marker is then driven into the ground at that point. However, as explained below, the process of accurately placing the stake 21 into the ground 22 as the desired point is problematic.
Specifically, once the operator has placed the target 13 and rod 11b in the correct location, the operator then sets the legs 18 into position and manipulates the tripod 12a until the rod 11b and target reflector 13 are plum or vertical. Typically, the tripod 12a may be equipped with a plumb bob or level (not shown). The receiver 15 communicating with the transit 10a may also communicate to the operator that the rod 11b and target 13 are plum or vertical. At this point, with the rod 11b and target 13 in a plumb or vertical position and after being assured by the transit 10a or target receiver 15 that the rod 11b and target 13 are in the correct location, the operator must then move the rod 11b to place a stake 21 in the ground 22 in the exact location from which the rod 11b has just been moved. To do this, the skilled operator will move the rod 11b, keep his or her eye on the spot on the ground 22 where the stake 21 should be placed, insert the state 21 into the ground, and then replace the rod 11b and tripod 12a back into the position to confirm that the stake 21 is in the correct position. Often, the operator does not place the stake 21 in the exact desired location and the stake 21 must be moved, and the process repeated until the correct location of the stake 21 is verified. This trial and error process is typically repeated a number of times before the accuracy of the placement of the stake 21 are confirmed.
Referring to FIG. 4, the use of a rod 11c and target 13 without a tripod is even more difficult. Target rods 11c without tripods typically may include a sharp distal end 23 that puts a preliminary visual mark on the ground 22. However, the preliminary mark may be difficult to see if the ground surface is rough, wet, grassy, etc. Further, ensuring that the rod 11c is plum or vertical can be time-consuming unless the operator is skilled or experienced. Typically, placing the stake 21 in the correct location also requires the same trial and error process described above in connection with FIG. 3.
Thus, even with the advent of EDM, GPS, electronic transits 10a, electronic target receivers 15 and target reflectors 13, one prominent problem associated with currently available targets 13 mounted on either rods 11c or tripods 12a lies in the trial and error process used by operators to accurately place the mark 21 into the ground. Obviously, the above procedure is cumbersome, repetitive and time consuming. These problems are exacerbated when dozens or hundreds of marks must be placed for larger tracts. As a result, there is a need for methods and apparatuses for more rapid and accurate marking of surveyed land.